Nearly all mail that is correctly addressed arrives at its destination within two business days of being sent. In fac...

When I worked this problem, I could only deduce that some mail was incorrectly addressed - not that a large portion was. For me it came down to not being able to determine what portion of the mail was damaged in transit. If most mail arrives in 3 days or longer, we do not know if that is caused by 1) not correctly addressing the mail or 2) the mail being damaged in transit. For example, if we have a total of 100 pieces of mail, 90 could be properly addressed, with 40/90 being damaged in transit. 50/90 of the properly addressed mail would arrive within 2 business days, meeting the first criterion. 40/90 would arrive later than 2 days as a result of being damaged in transit, meeting the second criterion. 10/90 would arrive later than 2 days as a result of being incorrectly addressed. In my mind, this scenario would eliminate D as an answer choice. To prove this logically: P: M - Most - Not Arrive In <= 2 Days *Most of all mail does not arrive in less than or equal to 2 days, since most mail arrives three business days or more after being sent P: MCA and Not DIT -> <= 2 Days * If mail is both correctly addressed and does not get damaged in transit, then it will arrive in less than or equal to 2 days ("Correctly addressed mail takes longer than this only when it is damaged in transit") Contrapositive of above: Not <= 2 Days -> Not MCA or DIT Combination of above premises: M - Most - Not <= 2 Days -> Not MCA or DIT Thus we can conclude that since most mail does not arrive in less than or equal to 2 days, most mail is EITHER not correctly addressed OR most mail is damaged in transit. We cannot conclude which has a greater impact, and thus we cannot conclude that a large proportion of mail is incorrectly addressed.